Weakness
Just as a human being may die of extreme sleep deprivation - a death preceded by total disorientation (Insanity) - an immortal sound can "die" when it is deprived of grace (by committing of mortal sin). "There is a sin that leads to death, " John reminds us (see 1 John 5:16).
This kind of spiritual death is also preceded by a kind of "spiritual insanity," of which there are two primary forms. The first type is a deadening of the conscience, an outrageous disregard of the heinousness of seriously offending the infinite majesty of God. The second is a total disregard of the unspeakable suffering from eternal hellfire that awaits the unrepentant sinner. Each of these two forms of spiritual insanity has a cure, and applied cures will revive the "dying" soul, restoring the life of grace.
The first cure is a "godly sorrow" that "brings repentance" (2 Cor 7:10). This kind of remorse is based on love for God whom one has offended, and is called perfect contrition. The second antidote (imperfect contrition) is a remorse for sin because of fear of punishment: "The wicked will not go unpunished" (Prv 11:21). This fear refers not just to any sanction (such as the embarrassment of appearing foolish), but God-assigned punishment. (This makes a supernatural contrition, even thought "imperfect.")
To assure that any act of contrition is authentic, one needs a "firm purpose of amendment" - intending to avoid sin and the near "occasions" of sin. This releases God's life-giving forgiveness.